1. Field of the Invention
The invention relates generally to broadcast systems and, more particularly, to authorization control methods and systems for direct broadcast satellite systems.
2. Description of the Related Art
When a user subscribes to a direct broadcast satellite (DBS) system, the DBS system must be capable of restricting the user's reception of video, audio or data content to only those portions of the DBS system for which the user has subscribed. DBS systems have generally restricted reception through selective authorization of channels. In the Hughes.sup..RTM. /DirecTV.sup..RTM. Digital Satellite System (DSS.sup..RTM.), because each receiver unit has a unique identification number, a control message sent from a central uplink facility via the satellite link can be individually addressed to each new user of the system to specifically authorize the receiver unit to process a particular channel or channel group.
Individually-addressed control messages have also been used outside of the initial subscription process to control channel authorizations on a more temporary basis. For example, the selective authorization of pay-per-view channels has been accomplished through such individually-addressed control messages.
In the DSS system, selective channel authorization in accordance with the above-described method has been accomplished by establishing two sets of eight bit flags. One set of bit flags is established for each subscriber in a memory contained within the receiver unit wherein the enabling of each bit flag represents an authorization for the subscriber to receive a particular channel or channel group. The other set of bit flags is established for each channel provided by the DSS system such that each bit flag represents whether the channel falls within one of the aforementioned channel groups. If corresponding bit flags in the two sets are both enabled, the subscriber may have access to the channel.
The individually-addressed control messages sent from the DSS uplink facility via the satellite link include commands to enable or disable one of the bit flags associated with each subscriber. Enabling a particular bit flag allows the subscriber to receive data for the development of an electronic programming guide (EPG) providing program information for the channels having a corresponding bit enabled. Moreover, the subscriber is also allowed to receive tuning instructions for each such channel. In this way, the above-described bit flag matching method has provided a first level of channel screening for the DSS system.
However, enabling and disabling the bitmap flags via individually-addressed control messages is not suitable for applications requiring the transmission of similar messages to large numbers of subscribers (e.g., one-half of the subscribers in a six million subscriber system). Large numbers of individually-addressed control messages would entail significant time to transmit or would consume significant amounts of bandwidth needed for the transmission of actual video, audio or data content. For the same reasons, the above-described method is also undesirable for applications involving dynamic channel authorizations.
Still further, in order to generate the individually-addressed control messages, it is necessary for the uplink facility to know the identification numbers of those subscribers that must be addressed. At times, the uplink facility may not know which subscribers must be addressed. For example, when a subscriber orders a particular service locally, the identification number of the subscriber will not be known until the locally-known information is transferred to the uplink facility.